Carburetors are equipments that mix the proportional fuel and air in a vacuum condition generated by an engine. The carburetor acted as an exact measuring apparatus plays an important role in the engine and thus is called as a “heart” of the engine. The carburetor apparatus includes a starting device, an idling device, a moderate load device, a full load device and an accelerator. According to different working status demands of the engine, the carburetor can proportion the corresponding concentration and output the mixed gas with corresponding quantity. To uniform the mixed gas, the carburetor can further atomize the fuel to support the normal operation of the apparatus.
While a rotary valve plunger type carburetor is one type of carburetors that changes the amount of fuel outputted by lifting or lowering a plunger. Commonly, a conventional plunger lifting mechanism of a carburetor includes rollers, plunger, cam and main measuring needle and the like. This plunger lifting mechanism is configured at outer top of the carburetor body, and the spiral surface is formed on the throttle wire bracket, and the lifting and lowering movement is driven by engaging the spiral surface with steel balls of the fixed plate. However, for this structure, scraps are easy to be accumulated at the spiral surface, to reduce the agility of the plunger. Furthermore, the movement of the plunger along the spiral surface has only supporting point, which may generate deflected force of the plunger, and bring problems such as the plunger is blocked and the plunger is not flexible.